Vaisala: Solar Performance Maps of the United States reveal considerable solar irradiance variability during the summer months, even in desert locations such as Nevada

Solar Performance Maps show high variability throughout June, July, and August based on 15+ year records and illustrate associated impact on project profitability

Las Vegas, Nevada, 23-10-2014 — /EuropaWire/ — Solar Performance Maps of the United States, released today by Vaisala, a global leader in environmental and industrial measurement, reveal considerable solar irradiance variability during the summer months, even in desert locations such as Nevada.

Furthermore, these findings have, in turn, demonstrated the need to make more informed use of long-term data to guarantee the ongoing performance and profitability of sites. At the 392MW Ivanpah Solar Power Facility site in Nevada, the world’s largest concentrated solar power (CSP) project, solar irradiance has been shown to have either exceeded or fallen short of expectations in 10 out of 15 summer months over the past five years – leading to annual performance fluctuations potentially worth US$440,000.

As the global photovoltaic (PV) and CSP industries mature and seek to become cost competitive with conventional energy sources, developers, operators, and lenders are increasingly required to make critical investment decisions which, ultimately, have a bearing on the future success of their expanding portfolios. Informed siting choices, resource assessment, and long-term energy modeling are a crucial part of ensuring profitability and return-on-investment.

Variations in solar irradiance caused by anomalous weather patterns are proven to have a substantial impact on the monthly and annual outputs of an asset and must be accounted for in early stage and ongoing performance estimates. However, the quantity and quality of irradiance data traditionally gathered by developers for this purpose has often proven inadequate.

It has become common practice to base long-term financial and operational decisions on one-year’s worth of TMY (Typical Meteorological Year) data. This strategy fails to account for inherent climatic variability over the project lifetime and puts assets at considerable risk of underperformance and subsequent loss of profitability in the long-term, especially considering that TMY datasets are based on a “normalized” year and actually screen out both extreme highs and extreme lows.

For more than 15 years, Vaisala 3TIER Services have been measuring and studying solar irradiance across the globe. Making use of this extensive dataset, over the past five years, the company has produced a Summer Solar Performance Map of the United States, analyzing solar irradiance variability during the three-month period when peak production is commonly expected.

These maps serve to graphically illustrate fluctuations in solar irradiance from long-term average levels, giving an indication of the inherent variability of the solar resource and demonstrating the influence of monthly weather patterns on project performance. Combined, they provide a tool developers can use to analyze and quantify the causes of over or underperformance.

During the 2014 study, for analysis purposes, the area surrounding the Ivanpah Solar Power Facility in Nevada was chosen as a case study. While desert regions typically enjoy more consistent solar resources, this year’s figures indicate a clear fluctuation in solar irradiance – 5% above average levels in June, but 5-8% below average in July and August.

Industry wide figures suggest that a 5% negative anomaly in solar irradiation during the summer months for a CSP or PV site can translate to a 1-1.5% decrease in annual revenue for a solar developer or operator, highlighting a clear industry requirement to take a more comprehensive approach to gathering long-term weather data.

“The impact of solar variability on the balance sheet can and will make the difference between profitability and loss,” said Richard Pyle, Energy Segment Director at Vaisala. “It therefore has a significant influence not only on individual project sites but also on the international standing of solar energy as a viable investment proposition, particularly as the industry expands into emerging markets overseas.”

Gwendalyn Bender, Energy Assessment Product Manager at Vaisala further added, “It is critical that developers acknowledge that resource variability occurs not just from month to month, but also from year to year. BrightSource Energy [the developer of Ivanpah] was ahead of its time when it first approached us in 2009 to help address this resource assessment issue. They took the long-view and saw a clear requirement to use more sophisticated long-term solar data and modeling techniques to guarantee ongoing site performance.”

To download a copy of the Summer 2014 Solar Performance Maps of the United States, please visit: Documents/Vaisala News Articles/Misc/2014 Solar Performance Map.pdf.

For more information about how Vaisala can help you make profitable long-term performance decisions, please visit us at Solar Power International 2014 in Las Vegas, Nevada, October 20-23, Booth #1451.

For further information:
Gwendalyn Bender
Energy Assessment Product Manager, Vaisala
+1 206 325 1573

Francesca Davidson
Energy Communications Expert, Vaisala
Tel +1 206 708 8544

About Vaisala
Vaisala is a global leader in environmental and industrial measurement. Building on 78 years of experience, Vaisala contributes to a better quality of life by providing a comprehensive range of innovative observation and measurement products and services for chosen weather-related and industrial markets. Headquartered in Finland, Vaisala employs approximately 1500 professionals worldwide and is listed on the NASDAQ OMX Helsinki stock exchange.


Vaisala: Solar Performance Maps of the United States reveal considerable solar irradiance variability during the summer months, even in desert locations such as Nevada

Vaisala: Solar Performance Maps of the United States reveal considerable solar irradiance variability during the summer months, even in desert locations such as Nevada


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